1. Field of the Invention
This invention relates to a process for removing the solid content (water-dispersible resin and the like) in a development waste liquor generated in the course of the printing plate making process using a photosensitive resin, particularly a liquid photosensitive resin printing plate and to apparatus for treating the development waste liquor.
2. Description of the Related Art
The development step carried out in the printing plate making process using a photosensitive resin is a step in which the photosensitive resin plate, the exposure of which has been completed, contacts an aqueous developer comprising a surface active agent as the main component by brushing, spraying or the like to dissolve the resin of the unexposed portion in the developer, thereby converting the latent image in the exposed portion to a visible image.
During repeating the above-mentioned development, the concentration of the resin dispersed in the developer increases, and when it reaches 2 to 4% by weight, the capacity of the developer deteriorates and causes problems such as uncured resin reatachably to the plate surface to deteriorate the quality of the printed image, make the development time remarkably long, and the like. Therefore, it becomes necessary to discharge the deteriorated developer and substitute therefor a fresh developer.
The development waste liquor thus discharged contains a photosensitive resin, a surface active agent (dispersing agent), a defoaming agent and the like, and the COD (chemical oxygen demand) becomes at least 5,000 mg/liter by the above materials.
As a general method for the treatment of the above development waste liquor, various techniques are known. However, as stated below, they are not sufficient as a method for easily and effectively removing the resin component contained in the development waste liquor.
(1) Flocculation
The resin component is precipitated by adding a complexing agent. However, the resin component is not solidified and hence care must be given to the handling of the ooze-like sediments.
(2) Ultrafiltration and Reverse Osmosis
The resin component in the development waste liquor tends to cause blocking of a membrane, and in some cases, the membrane life is remarkably shortened unless the solid content has previously been removed by flocculation or the like. When any of ultrafiltration and reverse osmosis is used alone, it is necessary to pay attention to the membrane life.
(3) Distillation
A high energy is necessary for the latent heat of vaporization of water, and the operating cost is high. Moreover, the solidified resin to be separated from the water content during evaporation blocks the evaporation piping and hence the heat transfer efficiency tends to be lowered. Accordingly, even in the case of this method, the removal of the resin component is considered to become necessary as a pretreatment.
(4) Incineration
The energy cost due to the latent heat of vaporization of water is high, similar to the above-mentioned distillation.
(5) Electrolysis
After the electrolysis, filtration is further necessary, and it follows that the treatment apparatus requires an electrolysis means and a filtration means (filter press or the like). Therefore, the apparatus cost becomes high.
Moreover, the filtered resin component is in the form of a sticky polluted sediment, so that care must be given to the handling of the same.
(6) Photo-oxidation
The development waste liquor is irradiated with an ultraviolet ray; however, when the ultraviolet irradiation is conducted in the state that the resin is dispersed, it is difficult to solidify the resin component in the development waste liquor and the precipitated resin component re-floats easily, and hence, attention should be paid to the filtration of the same.
As described above, if there is a method which can effectively separate the resin component dispersed in development waste liquor and by which the solidified resin component can be easily handled with inexpensive apparatus, such a method is effective as a pretreatment of the waste liquor treatment including ultrafiltration, reverse osmosis, electrolysis and the like.
This invention aims at solving the above-mentioned problems in the prior art and it is an object of this invention to provide a process for treating a development waste liquor by which the resin component contained in the waste liquor can be separated easily.
Another object of this invention is to provide apparatus for treating a development waste liquor.
Other objects and advantages of this invention will become apparent from the following description.
This invention includes the following:
(i) A process for treating a development waste liquor comprising a photosensitive resin and a surface active agent, which comprises subjecting the development waste liquor to a treatment for diminishing the efficacy of the surface active agent, thereby separating the resin component from the development waste liquor, thereafter irradiating the development waste liquor with an ultraviolet ray having a wavelength of 300 to 400 nanometers to cure the resin component in the development waste liquor and then removing the resulting solids. As the means for removing the resulting solids, filtration is preferable.
(ii) A process for treating a waste liquor generated in the step of the development of a photosensitive resin printing plate, which comprises heating the waste liquor which has dissolved therein a photosensitive resin and contains a nonionic surface active agent to a temperature not lower than the clouding point of the nonionic surface active agent, thereby separating the resin component from the waste liquor, thereafter irradiating the waste liquor with an ultraviolet ray having a wavelength of 300 to 400 nanometers and subsequently removing the resulting solids. As the means for removing the resulting solids, filtration is preferable.
(iii) A process for treating a waste liquor generated in the step of the development of a photosensitive resin printing plate, which comprises adding a flocculating agent to the waste liquor which has dissolved therein a photosensitive resin and contains an anionic surface active agent, thereby separating the resin component from the waste liquor, then irradiating the waste liquor with an ultraviolet ray having a wavelength of 300 to 400 nanometers and subsequently removing the resulting solids. As the means for removing the resulting solids, filtration is preferable.
In the above processes, when the nonionic surface active agent or anionic surface active agent and a liquid photosensitive resin comprising a prepolymer having reactive double bonds at its ends (ex. unsaturated polyurethane prepolymer) are used, the effect of this invention is particularly exerted.
(iv) An apparatus for treating a development waste liquor comprising a photosensitive resin and a surface active agent, which comprises a waste liquor treatment tank equipped with a heating means, a stirring means, an ultraviolet-irradiating means and a filtering means.